The present invention relates to a push actuator, and more particularly to a push actuator having a telescopic column formed with a pair of inter-spaced helical bands, one of which being supported with a ball support member.
U.S. Pat. No. 4,875,660 issued in 1989 to two of the co-inventors of the present invention, Pierre Gagnon and Pierre Laforest (hereafter the Gagnon patent), shows a push actuator to be used instead of a hydraulic cylinder. The Gagnon push actuator has the advantage of requiring less space than conventional hydraulic cylinders when in a contracted position, due to the fact that no concentric tube portions have to be stored within each other. Also, it can support a very heavy load, since it forms a cylindrical column when in an extracted position, without any concentric portions as with a hydraulic cylinder, and this vertical structure has a high vertical rigidity. Very important world-wide commercial success of the push actuator of the above-mentioned Gagnon patent has proven it to be a very advantageous alternative to conventional hydraulic cylinders.
The Gagnon push actuator generally works as follows. A hollow cylindrical rotor is rotatably carried over a base fixed to the ground. A motor selectively activates the rotor. A first horizontal band is vertically stacked in a helix and rests on the ground, while a second vertical band is horizontally stacked in a spiral, the latter located in an annular casing located co-axially around the rotor. The upper end of each band is fixedly attached to a platform, which is destined to be raised. When the rotor is rotated, each turn of the vertical band is guided and installed between two vertically successive turns of the horizontal band, to thus gradually form a vertical telescopic column. The load of the platform supported by the push actuator is induced through the vertical and horizontal band turns, to the idle rollers which support the horizontal band for one full helical turn.
One problem associated with the Gagnon push actuator resides in the load-bearing rollers used to support the horizontal band and the loaded platform. The rollers are indeed a very expensive component of the push actuator, and require significant space inside the rotor, which results in a diametrally larger push actuator.
It is the general object of the present invention to provide a push actuator capable of forming a telescopic column, which improves upon the prior art Gagnon push actuator.
It is another object of the present invention to provide a push actuator which has enhanced load-bearing elements to replace the cumbersome and expensive prior art rollers.
The present invention relates to a telescopic tube comprising:
a first annular band wound in helical form about a central axis with its turns transversely normal to said central axis and capable of taking a retracted stacked position with its turns resting flat against one another, and an extended position with its turns spaced from one another in the direction of said central axis;
a second band wound on itself, with its turns transversely parallel to said central axis and capable of taking a retracted, spiral position with its turns nested within one another and an extended position with its turns forming a helix around said central axis and generally equally radially spaced therefrom to form a tube, said first and second bands, when in retracted position, being in respective locations so as to clear each other;
a frame having a base resting on the ground and a rotor rotatably carried by said base;
a continuous frictionless support member carried by said rotor and forming at least a portion of a helix for supporting part of said first band, and for successively spacing the turns of said first band;
a power device, to cause relative rotation of said first band and of said rotor about said central axis, said continuous frictionless support member allowing the axially oriented load of said push actuator to be transmitted from said first band to said rotor while allowing a substantially frictionless relative rotation of said first band and said rotor; and
a guiding member to insert the turns of the second band between the spaced turns of the first band, with the edges of the turns of the second band bearing against the turns of the first band, the second band thus forming a spacer for the turns of the first band.
Preferably, said continuous frictionless support member includes a number of balls carried on a track carried by said rotor and forming at least a portion of a helix for supporting part of said first band, and for successively spacing the turns of said first band.
Preferably, said track has a first and a second ends, said continuous frictionless support member further comprising a ball re-circulation unit including at least one channel linking said track first and second ends for allowing said balls to engage said channel and consequently to circulate between said track first and second ends.
The present invention further relates to a push actuator having opposite first and second ends and an intermediate portion between said first and second ends, said push actuator further defining a central axis extending between said first and second ends and comprising:
a fixed base portion at said first end;
a rotor member rotatably carried by said base portion and rotatable about said central axis;
a power device, for selectively rotating said rotor member relative to said base portion;
a load-bearing member at said second end, movable relative to said first end, between a retracted position in which said load-bearing member is adjacent to said first end, and an extracted position in which said load-bearing member is distally located relative to said first end;
a first flat band being perpendicular to said central axis, being wound according to a helical pattern about said central axis, and having a first end portion adjacent said push actuator first end and a second end portion attached to said load-bearing member;
a second flat band being parallel to said central axis, being wound according to a helical pattern about said central axis, and having a first end portion adjacent said push actuator first end and a second end portion attached to said load-bearing member;
a continuous frictionless support member with at least a portion thereof being wound in a helical pattern about said central axis, with part of said first helical band engaging said continuous frictionless support member allowing substantially frictionless rotation of said rotor member relative to said first band; and
a guiding member at said push actuator intermediate portion and carried by said rotor member, for guiding said second band so as to place each turn of each one of said first and second bands between two successive turns of the other one of said first and second bands between said intermediate portion and said second end when said rotor member is rotated in a first direction around said central axis, thus forming a telescopic column composed of the interconnected first and second bands with the edges of the turns of the second band bearing against the turns of the first band, and with said first and said second bands each being independently stackable between said intermediate portion and said first end.
Preferably, said continuous frictionless support member forms a closed loop around said central axis and includes:
a track carried by said rotor member, wound in a helical pattern and having a first and a second ends;
a re-circulating unit including at least one inner channel linking said track first and second ends; and
a support medium capable of circulating along said track and through said re-circulating unit channel between said track first and second ends, with part of said first helical band engaging said continuous frictionless support member by bearing against said support medium for allowing substantially frictionless rotation of said rotor member relative to said first band.
Preferably, said continuous frictionless support member is a ball support member and said support medium is a number of balls engaging said track, with at least part of said first helical band engaging said balls for allowing substantially frictionless rotation of said rotor member relative to said first band.
Preferably, the portion of said first band which is located between said first end and said intermediate portion of said push actuator is stacked in a helical pattern, and the portion of said second band which is located between said first end and said intermediate portion of said push actuator is stacked in a spiral pattern.
Preferably, said portion of said second band which is stacked in a spiral pattern is stored in a second band magazine which is rotatably carried by either one of said base portion and said rotor member.
Preferably, said track of said ball support member forms n complete helical turns, with n being a positive integer.
Preferably, said track of said ball support member forms a single complete helical turn.
Preferably, said push actuator base portion includes a ground-bearing structure supporting a casing through the instrumentality of a universal joint allowing pivotal displacement of said casing relative to said ground-bearing structure, with said rotor member being rotatably carried by said casing.
Preferably, said push actuator is destined to be used with its central axis being vertically aligned and with said first end being located under said second end, said load-bearing member being a platform member including a top platform and a lower saucer linked to each other by means of a universal joint for allowing pivotal displacement of said top platform relative to said lower saucer, with said second ends of said first and second bands being attached to said saucer.
Preferably, said push actuator is destined to be used with its central axis being vertically aligned and with said first end being located under said second end, said track being supported by said rotor by means of a spring member fixedly carried by said rotor.
Preferably, said spring member is a leaf spring formed in a helical pattern and continuously supporting said track.
Preferably, said ball support track comprises two helical ball channels wherein two adjacent rows of balls are provided.
The present invention further relates to a push actuator having a vertical central axis, comprising:
a fixed base;
a selectively rotatable rotor carried by said base;
a power device for selectively rotating said rotor about said central axis;
a horizontal helical band having a lower portion stacked in a helical pattern and a helical upper portion;
a vertical band, having a lower portion stacked in a spiral pattern separately from said horizontal band, and an upper helical portion engaged by the upper portion of said horizontal band to form a vertical telescopic column;
a helical ball support track member carried by said rotor and including a helical track along which a number of balls can roll and slide, said track having an upper and a lower end, said horizontal band resting on said balls to allow rotation of the rotor member while the horizontal band remains rotatably stationary;
a ball re-circulation unit linking said track upper and lower ends and including ball channels engageable by said balls to allow said balls to circulate between said track upper and lower ends; and
a guiding member mounted to said rotor;
wherein upon rotation of said rotor, said vertical column is formed with the upper portions of said horizontal and vertical bands, by said horizontal band being lifted and its turns being spaced through its engagement on the rotating helical ball support track member, and by each turn of said vertical band being guided by guiding member to be inserted between two vertically successive turns of said horizontal band, with the edges of said vertical band bearing against said horizontal band.